For a moment, let's flashback to the Locard's exchange principle section. To reiterate, it basically expounds that every contact leaves a trace. What this means, in the digital context, is that all interactions with the digital system/network will leave some sort of an artifact/data behind as evidence of this event. These artifacts are known as digital footprints. They are of the following two types:
Passive
Active
Passive digital footprints are created by the system without the knowledge of the user, such as in the case of pasting passwords from a file to an application evidence or copies can be found in the volatile memory. Cookies are another example of this.
The user creates active digital footprints deliberately, such as in the case of a Facebook post, sending an e-mail, or storing and transmitting pictures.
These will usually exist and can be recovered from the following:
Device memory
Disk space including logs
Network traffic capture
